Imitation in children has long been recognized as a developmentally significant behavior related to aspects of social cognition, memory, and learning. Though evidence for individual differences in imitative behavior has become plentiful in recent years, very little research to date has sought to explore the nature of these differences and their potential bases. The goal of the proposed research is to investigate individual differences in imitation from a behavioral genetic perspective; that is, to examine the potential genetic and environmental factors underlying the observed variability in imitative expression. This study will use a twin design to examine both elicited and spontaneous imitation in children at age 24 months. 200 pairs of twins will participate in a series of laboratory -based tasks including three multi-step, sequential imitation items modeled by an adult experimenter. Performance on these items, as well as spontaneous imitation behaviors assessed during the laboratory visits, will be analyzed using both correlational and model-fitting procedures to determine the relative contributions of genes and environment to elicited and spontaneous imitation performance. In addition, temperament and cognitive performance will be analyzed to determine their potential relationship to the observed variability in imitation. [unreadable] [unreadable] [unreadable] [unreadable]